The invention relates to hinge joints in general, and more particularly to improvements in hinge joints which can be used in the seats of motor vehicles to facilitate changes of inclination of the back rest relative to the body-supporting part of the seat, particularly a driver's seat or the seat next to the driver's seat.
It is well known to design the hinge joint for use in the seat of a motor vehicle in such a way that the component which is attached to or forms an integral part of the back rest is pivotable relative to the component which is fixed to or is integral with the body-supporting part in response to angular movement of a pintle which can be rotated by a hand wheel or by a motor in order to permit or initiate an angular movement of a gear on the pivotable component relative to a mating gear on the other component of the hinge joint. As a rule, the pintle comprises eccentric portions which are spacedly surrounded by one of the components and its gear, and such gear can be urged radically by a resilient member which is stressed in the axial direction and is normally an annular body which surrounds the pintle.
In accordance with a presently known proposal, one of the components has a spur gear which is formed by shifting a portion of the component axially of the pintle so that the thus obtained active spur gear causes the respective component to develop a complementary passive gear which is an internal gear at the other side of the respective component. Reference may be had to commonly owned U.S. Pat. No. 4,563,039 granted Jan. 7, 1986 to Jorg for "Hinge joint for use in the seats of motor vehicles and the like". The other component has a complementary active internal gear with a number of teeth exceeding by one or more the number of teeth on the active spur gear so that the two active gears can move radially of each other, i.e., the active spur gear can move within the confines of the active internal gear. The active spur gear surrounds a first eccentric portion of the pintle. The just described hinge joint further comprises a segmented washer-like spring which extends into the passive gear of the one component. The spring is mounted on a second eccentric portion of the pintle, and the apex of the second eccentric portion is engaged by the adjacent segment of the spring. The apices of the two eccentric portions must be located in a common plane which includes the axis of rotation of the pintle. The eccentricity of the second eccentric portion of the pintle is more pronounced than that of the first eccentric portion. When the pintle is rotated, the spring segment which engages the apex of the second eccentric portion can yield in the axial direction whereby the entire spring, and hence the corresponding component of the hinge, moves in the radial direction to eliminate radial play between the mating teeth of the two gears. A drawback of the just described hinge joint is that the pintle must be sufficiently long to be provided with two eccentric portions as well as that the pintle is more complex and more expensive than a pintle with a single eccentric portion.